Works fine on our demo site below. My best guess is there are no gallery images available, you've a JS conflict preventing the gallery selection from displaying, or you've a CSS conflict causing the gallery to remain hidden. Are there any fatal JS errors (they'll be red) present in your browsers developer tools (press F12 to open) under the Console tab?
demo.cbdemosites.com/
Note custom canvas gallery images should be placed in the below location unless the path parameter has been supplied to point to a different folder.
/images/comprofiler/gallery/canvas
They should be of type jpg, png, or gif and have alphanumeric filenames. Ideally you should also supply a thumbnail for each gallery image. Thumbnails should be smaller with an approach 100px height and be named the same as full size except prefixed with "tn".